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Jun 14th, 2026
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Joined: Jun 2019
Posts: 810 Likes: 59
Talk Morgan Regular
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OP
Talk Morgan Regular
Joined: Jun 2019
Posts: 810 Likes: 59 |
When I press on the brake pedal the brake lights work fine. However, when the headlights are on and I press the brake pedal, one brake light gets brighter, and the other goes off. It's only a problem when I have the headlights on.
Any idea where to start looking?
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Joined: Nov 2018
Posts: 6,680 Likes: 441
Talk Morgan Sage
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Talk Morgan Sage
Joined: Nov 2018
Posts: 6,680 Likes: 441 |
I'd start with the earths. I've had some really wierd stuff happen due to earth issues!
"Y mae dafad ddu ym mhob praidd"
1972 4/4, 1981 MGBGT, 1984 FLHT1340, 1980 XLH1000, 1990 ZX10
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Joined: Feb 2016
Posts: 8,705 Likes: 416
Needs to Get Out More!
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Needs to Get Out More!
Joined: Feb 2016
Posts: 8,705 Likes: 416 |
That's a good one! Putting the headlights on would also turn on rear sidelights. Check all associated rear wiring particularly shared ground connections as it looks like issue is being caused by unintended electrical secondary paths.
Richard
2018 Roadster 3.7
1966 Land Rover S2a 88
2024 Royal Enfield Guerrilla 450
1945 Guzzi Airone
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Joined: May 2014
Posts: 5,442 Likes: 133
Black Rat Charter Member
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Black Rat Charter Member
Joined: May 2014
Posts: 5,442 Likes: 133 |
Probably a faulty side light bulb, start by putting some new bulbs in. I f your brake light bulbs are dual filament it's probably one of them.
Keith
2013 narrow bodied + 4 Ruby.
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Joined: Jun 2019
Posts: 810 Likes: 59
Talk Morgan Regular
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OP
Talk Morgan Regular
Joined: Jun 2019
Posts: 810 Likes: 59 |
I will look at the earths. I think I have to pull the spare out to find the connections.
I did test the bulbs with an Ohm meter and they checked out OK, but I thought I would change them first since that is the easiest thing to do.
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Joined: Nov 2018
Posts: 6,680 Likes: 441
Talk Morgan Sage
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Talk Morgan Sage
Joined: Nov 2018
Posts: 6,680 Likes: 441 |
My money is that it's the opposite light to the one that's doing wierd stuff - possibly a bullet pulled out of a connector......
"Y mae dafad ddu ym mhob praidd"
1972 4/4, 1981 MGBGT, 1984 FLHT1340, 1980 XLH1000, 1990 ZX10
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Joined: Oct 2019
Posts: 5,608 Likes: 617
Charter Member
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Charter Member
Joined: Oct 2019
Posts: 5,608 Likes: 617 |
Could be the connection in the bulb holder even if the bulbs check out fine off the car .... cleaning the solder contacts on the bulb bases and the sprung pins in the holders is never wasted time.
K
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Joined: Jun 2019
Posts: 810 Likes: 59
Talk Morgan Regular
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OP
Talk Morgan Regular
Joined: Jun 2019
Posts: 810 Likes: 59 |
The bulb connections looked fine.
I have to locate the bullet connections. Not sure if they are under the spare, or under the boot.
Last edited by PaulyG; 29/06/22 12:32 PM.
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Joined: Jun 2019
Posts: 810 Likes: 59
Talk Morgan Regular
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OP
Talk Morgan Regular
Joined: Jun 2019
Posts: 810 Likes: 59 |
I replaced the bulbs and inspected the sockets. All good.
I checked all the connections in the rear of the car and everything seems fine there. And all the Earth's look good to. I checked ohm readings from earth in the socket to the frame and that is good.
When I have both bulbs out I checked the sockets with a meter, and everything there is working properly.
The issue is when the side lights are on and the brake pedal is pushed. It must be a problem with one wire somewhere, but I haven't found it yet
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Joined: Jun 2011
Posts: 82
Just Getting Started
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Just Getting Started
Joined: Jun 2011
Posts: 82 |
Could it be your hydraulic Brake light switch, checked earthing there? Example, pics and all sorts. https://www.gomog.com/allmorgan/brakelightswitch.html
ABBO
Morgan 2005 Roadster
Morgan 1986 4/4 4str Prev
Morgan 1953 +4 DHC Prev
Flippin Pongo 3008 Hybrid
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